LOS ANGELES — YouTube says more than 1 billion people are now visiting its online video site each month to watch everything from zany clips of cute kittens to sobering scenes of social unrest around the world.

The milestone was announced Wednesday at a splashy event in Santa Monica that was aimed at advertisers and featured performances from some of the website's biggest stars, such as the bands CDZA and Monsters Calling Home. It marks another step in YouTube's evolution from a quirky startup launched in 2005 to one of the most influential forces in today's media landscape.